Light-sensitive,photographic silver halide emulsion

ABSTRACT

BENZOXAZOLINE   2-(R2-N&lt;(-C(=S)-Z2-C(=CH-CH=)-C(=O)-)),3-R1,5-CL,6-CH3-   WHEREIN R IS HYDROGEN OR LOWER ALKYL RADICAL: R1 AND R2 INDIVIDUALLY MEAN LOWER ALKYL, LOWER ALKENYL, SUBSTITUTED ALKYL SELECTED FROM THE GROUP CONSISTING OF HYDROXY ALKYL, ACETOXY ALKYL, CARBOXY ALKYL AND SULFO ALKYL OR ARYL RADICAL; Z1 IS AN ATOMIC GROUPING WHICH CAN FORM, TOGETHER WITH THE ADJACENT NITROGEN AND CARBON ATOMS, A FIVE- OR SIX MEMBERED HETEROCYCLIC RING; Z2 MEANS OXYGEN, SULFUR OR A RADICAL =NR3 (IN WHICH R3 IS LOWER ALKYL OR CARBOXY-ALKYL RADICAL); X IS AN ACID RESIDUE, PROVIDED THAT X MAY NOT EXIST IF THE SUBSTITUTED ALKYL RADICAL TAKEN FOR R1 OR R2 IS CAPABLE OF FORMING, TOGETHER WITH AN ADJACENT NITROGEN ATOM, AN INTRAMOLECULAR SALT; AND M IS EQUAL TO 0 OR 1.   A LIGHT-SENSITIVE, PHOTOGRAPHIC SILVER HALIDE EMULSION WHICH CONTAINS, AS A SENSITIZER, A COMPOUND OF THE GENERAL FORMULA BENZOXAZOLINE)+ X(-) OR   (2-(R3-N&lt;(=C(-(CH=C(-R))M-CH=)-Z1-)),3-R1,5-CL-6-CH3-

Jan. 16, 1973 SHUI SATO ETAL 3,711,288

LIGHTSENSIIIVB, PHOTOGRAPHIC SILVER HALIDE EMULSION Filed Dec. 1, 1970 FIG. 1

' WAVE LENGTH (my) WAVE LENGTH (m x) United States Patent Int. Cl. Gtl3c 1/16 US. Cl. 96-132 7 Claims ABSTRACT OF THE DISCLOSURE A light-sensitive, photographic silver halide emulsion which contains, as a sensitizer, a compound of the general formula wherein R is hydrogen or lower alkyl radical: R and R individually mean lower alkyl, lower alkenyl, substituted alkyl selected from the group consisting of hydroxy alkyl, acetoxy alkyl, carboxy alkyl and sulfo alkyl or aryl radical; Z is an atomic grouping which can form, together with the adjacent nitrogen and carbon atoms, a fiveor six membered heterocyclic ring; Z means oxygen, sulfur or a radical =NR (in which R is lower alkyl or carboxy-alkyl radical); X is an acid residue, provided that X may not exist if the substituted alkyl radical taken for R or R is capable of forming, together with an adjacent nitrogen atom, an intramolecular salt; and m is equal to 0 or 1.

This application is a continuation-in-part of application Ser. No. 652,599 filed July 11, 1967, now abandoned.

This invention relates to a light-sensitive, photographic silver halide emulsion containing a new sensitizing dye. More particularly, this invention is concerned with a light-sensitive, photographic silver halide emulsion sensitized with a symmetrical or unsymmetrical polymethine dye or a merocyanine dye, both of which dyes are featured by having a specific benzoxazole ring of the general formula mentioned later.

In the prior art for sensitization of photographic silver halide emulsions, several polymethinecyanine dyes having a benzoxazole ring (typically those having strong sensitizing efiFect have been used). However, they disadvantageously cause an adverse influence upon the quality of photographic layer after its having been developed.

We have now found that a light-sensitive, photographic silver halide emulsion can be sensitized, without any undesired side effect, by use of a sensitizing dye which has a monoor polymethine chain terminated at its one end with a new heterocyclic ring. sensitizing dyes (compounds) useful in this invention can be represented by the following general formula 3,711,288 Patented Jan. 16, 1973 wherein R means hydrogen or lower alkyl radical; R and R individually mean lower alkyl, substituted lower alkyl, lower alkenyl or aryl radical; Z means an atomic grouping which can form, together with the adjacent nitrogen and carbon atoms, a 5- or 6-membered heterocyclic ring; Z means :0, 8 or =NR (in which R is lower alkyl or carboxyalkyl radical); X means an acid residue, provided that X may not exist if the substituted alkyl radical taken for R or R is capable of forming, together with the adjacent nitrogen atom, an intramolecular salt; and m is zero or 1. These sensitizing dyes can be characterized as methine dyes having a new benzoxazole ring, that is, 5-chloro-6-methyl-benzoxazole ring.

In the above formulas, suitable as R, and R are lower alkyl radicals, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, etc.; lower alkenyl radicals, e.g. allyl; substituted lower alkyl radicals, e.g. fi-hydroxyethyl, -hydroxypropyl or the like hydroxyalkyl, B-acetoxyethyl, 'y-acetoxypropyl or the like acetoxyalkyl, carboxymethyl, fl-carboxyethyl or the like carboxyalkyl, B-sulfoethyl, 'y-sulfopropyl, fi-sulfobutyl or the like sulfoalkyl; and aryl radicals typically including phenyl.

Typical examples of 5- or 6-membered heterocyclic rings represented by are as follows:

Thiazoles:

Thiazole, 4-methyl-thiazole, 4,5-diphenylthiazole, etc. Thiazoline Benzothiazoles Benzothiazole, S-methyl-benzothiazole, S-chlorobenzothiazole, 6-ethoxy-benzothiazole, 5,6-dimethylbenzothiazole, etc.

Naphthothiazoles a-Naphthothiazole, fi-naphthothiazole, etc. Selenazoles:

Selenazole, 4-methyl-selenazole, etc. Benzoselenazoles:

Benzoselenazole, S-methyl-benzoselenazole, S-chlorobenzoselenazole, etc. Naphthoselenazoles:

a-Naphthoselenazole, ,B-naphthoselenazole, etc. 3 S-dialkyl-indolenines:

3,3-dimethyl-indolenine, etc. Benzimidazoles Benzimidazole, S-chloro-benzimidazole, 5,6-dichlorobenzimidazole, S-methoxy-benzimidazole, S-carboethoxy-benzimidazole, etc.

2-quinoline 3 Oxazoles:

Oxazole, 4-phenyl-oxazole, 4,5-diphenyl-oxazole, etc. Benzoxazoles Benzoxazole, S-methyl-benzoxazole, S-methoxy-benzoxazole, 5-phenyl-benzoxazole, 5-chloro-benzoxazole, 6methyl-benzoxazole, 5-chlor0-6-methylbenzoxazole, etc.

Naphthoxazoles:

a-Naphthoxazole, B-naphthoxazole, ,fLH-naphthoxazole,

etc.

Typical as acid residues X are those which are common in conventionally known cyanine dyes, for example, Cl, Br, I, C104, B134, SO4CH3, SO4C2H5,

etc.

As apparent from the above description, the gist of the present invention resides in use, as a sensitizer, of a polymethine dye or a polymethine-merocyanine dye having a particular new benzoxazole ring which is substituted with chlorine and methyl at its 5- and 6-positions, respectively. It is to be understood that the existence of S-chlorine atom and 6-methyl group in the benzoxazole ring can successfully diminish undesired color-remaining property of the conventionally known benzoxazole ring type polymethine or polymethine-merocyanine dye, without sacrificing desirable high sensitizing activity of said dye. Thus, a light-sensitive photographic silver halide emulsion of the present invention is entirely free from staining of a photographic layer after development, said staining being occasionally observed when a photographic emulsion contains the known sensitizing dye. Further, new sensitizing dyes referred to in this invention have no adverse influence on the photographic properties of a silver halide emulsion to which said dye is to be added.

Now typical synthetic examples will be given below to indicate synthesis of some intermediates useful for the preparation of new sensitizing dyes of this invention and further to indicate synthesis of some of these sensitizing dyes.

Synthesis of intermediates NHCOCH:

4-chloro-6-amino-m-cresol (150 g.) is added to 500 ml. of acetic anhydride over about one hour, with stirring, which is then continued for additional 30 minutes. To the resulting solution, 500 ml. of Water is poured. The resulting mixture is cooled, and the separated crystalline mass is collected by filtration and Washed with water. 180 g. of a white crystalline product (with a small amount of diacetyl compound) having a melting point of 192- 196 C. is obtained. This product can be recrystallized from ethanol. M.P. 211 C.

Calculated for C H O NCl (percent): C, 54.16%, H, 5.05%, Found (percent): C, 53.99%, H, 528%.

150 g. of S-chloro-4-methyl-2-hydroxy-acetanilide is fused by heating at more than 200 C. thereby to remove moisture, and then subjected to vacuum distillation to collect a fraction having B.P. 148 C./ 36 mm. Hg. From this fraction, 120 g. of a white crystalline product having M.P. 92 C. is obtained.

Calculated for CgHsONCl (percent): C, 59.51%, H, 4.44%; Found (percent): C, 59.20%, H, 4.94%.

0 [HI] CH3 CH 01 N/ a SOs-Q-CHQ 9.1 g. of 2,6-dimethyl-5-chloro-benzoxazole and 10.5 g. of ethyl p-toluenesulfonate are heated in a sealed tube at 1 10 C. for 30 hours. The resulting mixture is washed with acetone and ether to collect 18 g. of a white crystalline product, which can be recrystallized from ethanol to give 15 g. of a pure product having M.P. 198 C.

CIIH2CH2CH2SO3- 9.1 g. of 2,6-dimethyl-S-chloro-benzoxazole and 6 g.

of 1,3-propanesultone are mixed. The mixture is heated at C. for 7 hours and then Washed with ether and acetone to recover 15 g. of a greyish white crystalline product.

Synthesis of new sensitizers 0.635 g. of 1-methyl-2-thi0quinolone-methyl iodide and 0.765 g. of 2,6-dimethyl-5-chloro-3 ethyl-benzoxazoliump-toluenesculfonate are dissolved in 10 ml. of ethanol. The resulting solution is added with 0.5 g. of triethyl amine and then refluxed on a water bath for 15 minutes. After cooling the solution, the resulting coloring matter is separated by filtration and recrystallized from methanol to obtain 0.06 g. of yellow crystalline needles, M.P. 298 -299 C. max. 452 mu (in MeOH).

CH3 /O\ CH S\ ilif 3] CH3 0 O\ cn c=on 01 \N has 3.82 g. of 2,6-dimethyl-5-chloro-3-ethylbenzoxazoliump-toluenesulfonate and 2.4 g. of ethyl orthoacetate are dissolved in 10 ml. of pyridine. The resulting solution is added with 0.5 g. of triethyl amine and then heated under reflux on an oil bath for one hour. To the resulting mixture, an aqueous potassium iodide solution is added to eifect precipitation of a coloring matter, which is recovered by filtration and recrystallized from methanol. 0.5 g. of a greenish red crystalline product is obtained. M.P. 266 C. A max. 502 Ma (in MeOH).

(BHzCHzCHzCHaSOaH QHzCHzCHzCHaSOy' CH CH5 mixture is heated under reflux on an oil bath-for 90 minutes. Thereafter, this mixture is cooled and shaken with ether. The ethereal layer is moved by decantatlon. The residual mass is treated, with warming, with ethanol. A coloring matter which precipitates from the ethanol soluttion by cooling is collected and washed with ethanol. The thus obtained crude product (1.1 g.) is dissolved in ethanol and then reprecipitated by the addition of ethanolic hydrochloric acid. After well washing with ether, a reddish orange crystalline product (1 g.) is obtained, which has M.P. 275 C. and A max. 504 III/.4 (in MeOH).

o s o 9] Hg r' mmv l am em,

0.77 g. of 2,6-dimethyl-5-chloro-3-ethylbenzoxa2olinm5 p-toluenesulfonate and 0.7 g. of 2-anilinovinyl-3-methyl thiazolim'um iodide are added to 5 ml: of pyridine and the mixture is heated under reflux on an oil bath for 3 hours. After cooling, the resulting solution is added with ether and ethanol thereby to have a coloring matter separated, which is then collected by filtration and recrystallized from methanol. 0.21 g. of an orange colored crystalline product is obtained. M.P. 300 C. A max. 472 m, (in MeOH). Y

on an oil bath for 2 hours. After cooling, the mixture is treated with ether to have a coloring matter separated,

which is collected by filtration and recrystallized from.

ethanol. 0.13 g. of reddish crystalline needles are. obtained. This product has M.P. 270 C. and A max. 52 my. (in MeOH).

1.22 g. of 2 anilinovinyl 5 chloro-6-methyl-3-ethylbenzoxazolium-p-toluenesulfonate, 0.8 g. of anhydro-lethyl-Z-methyl-3-.( -sulfopropyl) 5 chloro-benzimidazolium hydroxide, 0.5 g. of anhydrous potassium acetate and 10 ml. of acetic anhydride are mixed with well grind ing. The mixture is heated on an oil bath at 150 C. for

20 minutes.- After cooling, the resulting coloring matter is collected byfiltration and then recrystallized from methanol. 0.35 g. of a reddish orange colored crystalline product is obtained. M.P. 30 0 C.. A max. 485m (in MeOH). I r

0.41 g. of anhydro-Z-anilinovinyl-6-methyl-5-chloro-3- ('y-snlfopropyl)-benzoxazoliuni hydroxide and 0.25 g. of 3-ethyl-rhodanine are dissolved in 10 ml. of pyridine. The resulting solution is added. with 0.5 g. of triethyl amine and then heated under reflux on an oil bath for 90 minutes. After cooling,--the solution is treated with ether to have a coloring matter separated which is .thencollected by filtration and recrystallized from ethanol. 0.36 g. of a yellowish brown crystalline product is obtained. M.P. 213 C. A max. 490 m (in MeOH).

0.73 g. of 2-anilinovinyl-6-methyl-5-chloro-3-ethylbenzoxazoliurn-p-toluenesulfonate and 0.3. g. of 3-ethyl- 2-thio-2,4-oxazolidene'-3,S-dione are mixed into a liquid consisting of 5. 1 nl. of pyridine and 0.3 g. of triethyl amine. The resulting mixture is heated 'iunder'refiux on an oil bath for 45 minutes. The solution obtained is cooled and then added with petroleum ether thereby to have a coloring matter separated, which is collected by filtration and then recrystallized from a pyridine-methanol mixture. 0.35 g. of yellow, crystalline needles are obtained. This product has M.P."278 C. and A max. 473 my. (in MeOH).

ml. of pyridine added with 0.3 g. of triethyl amine) is heated under reflux for 45 minutes. After cooling the mixture, 20% hydrochloric acid is added thereto. The thus separated coloring matter is collected by filtration and washed with water. The crude product is purified -bydisSolving inv triethyl amine-added hot ethanol and reprecipitating with alcoholic HCl. 0.3 g. of an orange colored crystalline product is obtained, which has M.P. 231- C. and A max.-492 my. (in MeOH).

/oH=oH-NH- SO3CH3 Cl I I I 7.7 g. of 2,6-dimethyl-5-chloro-3-ethyl-benzoxazoliump-toluenesulfonate and 4 g. of diphenyl formamidine are fused together at 140-160 C. for IO'minutes. The resulting reaction mixture is added with ethanol and cooled. The separated crystals are collected by filtration and recrystallized from methanol, 5.8 g. of yellow crystalline needles are obtained M.P. 237 C.

CH=OHNH 1 l?/ CHzCHzCHzSOr 6.5 g. of anhydro-2,6-dimethyl-5-chloro-3-(-sulfopropyl)-benzoxazolium hydroxide and 4.2 g. of diphenyl formamidine are fused together at l40160 C. on an oil bath for minutes. To the reaction mixture, ethanol is added. The separated crystals are collected by filtration and washed well with hot ethanol. A yellow powdery 20 product, 2 g., is obtained. M.P. 300 C.-

3.5 g. of 2,6-dimethyl-5-chloro-3-ethyl-benzoxazoliump-toluenesulfonate and 1.8 g. of ethyl-isothioacetanilide are mixed by heating at 160 C. on an oil bath for 20 minutes and then added with ethanol. After cooling the resulting solution, separated crystals are collected by' filtration and then recrystallized from ethanol. 1.6 g. of yellowish orange-colored crystalline prisms are obtained. M.P. 210 C.

The compounds which are defined in the present in- 'vention are useful as sensitizers not only for white-black photographic materials but also for green-sensitive photographic emulsion for color photography. There is not observed any interaction between the sensitizers used and the color formers contained. The sensitizing dyes of the present invention do not cause fogging and do not diffuse to the adjacent layer in a photographic element. Therefore, these sensitizing dyes are particularly useful for dye sensitization of the green-sensitive photographic emulsion. Symmetrical cyanine dyes taken from the scope of this invention are particularly recommendable because of their good compatibility with color formers.

The amount of the sensitizing dye to be added will vary depending on the type of emulsions and the degree of sensitization desired, but it usually is within the range of from 10 mg. to 300 mg. per mole of silver halide contained in emulsions. It is desirable to add the sensitizing dye in solution dissolved in a suitable solvent, e.g. methanol or dimethyl sulfoxide. Preferably, the addition of the sensitizing dye into the emulsion is made just before completion of the second ripening of said emulsion. In this case, the emulsion to which the sensitizing dye of this invention is to be added may have been sensitized by way of gold-, sulfuror other chemical sensitization or supersensitization. The existence of any anionic surface active agent in the emulsion does not cause any problem.

As apparent from the above, a light-sensitive, photographic silver halide emulsion according to the invention is far more excellent than the conventional emulsion because it is entirely free from staining and residual color which occasionally take place after development and fixing.

Now the present invention will be explained in detail in conjunction with the following examples.

EXAMPLE 1 A light-sensitive photographic silver iodobromide emulsion containing 5% by mole of silver iodide is prepared according to a neutral process. This emulsion g.) is subjected to second ripening. Just before the completion of said ripening, the emulsion is added with an optimum amount (2 ml.7 ml.) of a methanolic solution of the below-specified compound (10 molar cone). The thus sensitized emulsion is coated on a film base and dried. The resulted light-sensitive photographic film is exposed to light according to a I IS method K-7'609 and then developed with a D-72 developer. Sensitization maximum of individual samples as well as absorption maximum (in methanol) of the used compounds are set forth in Table 1. Measurement of spectral sensitivity is made by using a diffraction lattice type spectrophotometer (with a light source of 2848 K.) manufactured by Shimazu Mfg. Co., Ltd., Japan.

Sensl. Abs.

Compound max. max.

Number R R R' X (my) (m 1 CH H CH: 525 496 S 0 CH 2 CzHs H CIHs 545 196 S0 CH:

C2115 zHa I 550 502 (CH hCOO H (032)2(300' 530 498 HMSOQH CH3 HmSOa- 530 502 (CHghSOgH CzHs (CH:)4SO3 560 504 I OH O\ N -CH-CH=CH 01 N f N Cl Sensi. Abs. Compound max. max. Number R R R X (m (m CzH C7H5 CQHE I 530 478 2 (3:115 (CH2)3S Oz 540 483 C2115 C2115 (011933 03 540 482 CH2); S O C ll O 11 520 478 2)aSOa C2H5 (CI-193$ 0 H 525 484 (CHmSOr (CH2)10 COOH; CzHa 540 483 I O N CH o1 CHCH=CH 01 N N 01 Sensi. Abs. Compound max. max. Number R R R (mg) (mp) GEES CzH5 (CH2)3S O3 560 490 02H! C2H5 (CH2)4 S O a 560 492 zHs (CH2)3O CO CH3 (CH2)4S O3" 540 494 (C 1); S Or 2H H3 555 488 onmsor (013930000113 (011:)48 03H 530 496 21 (0 93 S Oa 02H; (0H,); s 03H 560 492 s 0 CH3 CH3 =CHC=CH G1- /r CH3 N N I I X Sensi. Abs.

max. max. Compound Number R R R X (mp) (my) 22 CaH5 CH1; CaHs 600 528 23 C2115 CH: (OHmS 03- 600 531 =0 HCH=CN l O=C-N R Sensi. Abs

. max. max. Compound Number R R" R (m (my) 24 0,11 omo 0 OH Q 545 492 25 (OHM S O 11N061 02H; 545 490 O O\ lik ns-{Mil P Sensitization maximum 550 m Absorption maximum 505 m (in MeOH) Sensitization maximum 550 mu Absorption maximum 460 m (in MeOH) The photographic properties of the same silver iodobromide emulsion added with the control compound A or B are shown in Table 2, wherein a photographic speed 11 is expressed as a relative value based on the white or green light sensitivity of the control compound, which sensitivity is rated as 100.

TABLE 2-(1) [With reference to the control compound A] Amount Relative Relative Compound used (cc/10D g. speed to speed to used emulsion) White light green light Fog 4 102 91 (l. 02 4 103 '89 0. 03 9 100 103 0. 03 A (control) 5 100 100 0. 04

TABLE 2-(2) [With reference to the control compound B] Amount Relative Relative Compound used (ca/100 g. speed to speed to used emulsion) white light green light Fog 5 100 150 0. 03 5 107 141 0. O3 4 100 140 U. 02 5 108 143 0. D3 4 100 135 0. 03 5 105 131 0. O3 24 5 110 141 0. 02 B (control) 5 100 100 0. 03

In the above comparison test, the samples added with control compound A or B show undesired magenta color after the development and fixation of these samples even when sufficient rinsing is made. In contrast to this, the samples added with any one of the sensitizing dyes according to this invention is clear and do not sutfer from residual color.

EXAMPLE 2 A light-sensitive silver chlorobromide emulsion for low-speed photographic positive is added with a methanolic solution containing at M concentration one of various compounds indicated in Table 3 and then coated on a baryta paper and dried to obtain a sample which is a light-sensitive photographic paper. The photographic properties of each test samples are set forth below.

TA B LE 3 Amount Relative Relative used speed to speed to Residual Compound (co/100 g. white green color used emulsion) light light Fog density In FIG. 2 of the attached drawing, a spectral sensitivity curve of the silver chlorobromide emulsion used in this example and not added with any sensitizer is indicated by chain line and that of the same emulsion but added with the compound No. 9 according to the present invention is indicated by solid line.

EXAMPLE 3 To each 100 g. of a high-speed photographic silver indobromide emulsion prepared according to a neutral process, the compounds No. 4 and No. 9 and the control compound A are added respectively in the amount of 5 cc. of the methanolic solution with the 10" M concentration. The resulting three emulsions are individually added with 1-(4-phenoxy-3-sulfophenyl)-3-heptadecyl-5- pyrazolone as color former in the manner known per se and then adjusted to pH 6.8.

Each one of the thus obtained green-sensitive emulsions are divided to two portions, one of which is immediately coated on a film base to obtain a film sample and the other is coated, after incubation at 40 C. for 3 hours, on a same film base to obtain another film sample. A plurality of the samples thus prepared are exposed to green light according to a 118 method K-7609 and there- 12 after treated by color development, bleach and fixing. The sensitometric results of these samples are set forth in Table 4.

A high-speed photographic silver iodobromide emulsion containing 5% by mol of silver iodide and by mol of silver bromide is subjected to second ripening (chemical ripening). Just before initiation of the ripening, the emulsion is charged with a mixture of 5 ml. of a 0.1% aqueous sodium thiosulfate solution and a 1.0 ml. of a 0.1% aqueous HAuCl -4H O solution, based on mol of the silver halide, as a gold-sulfur sensitizer. The resulting emulsion is incubated at 55 C. for 60 minutes.

After completion of the ripening, the compound No. 11, 16, 21 and a compound B (control) are added respectively, in the form of a methanolic solution (l=0 molar conc.) at the amounts as set forth in Table I, to each g. of the emulsion, and then an optimum amount of 4-hydroxy 6 methyl-l, 3,3a,7 tetrazaindene is added thereto. Each of the emulsions thus obtained is coated on a film base and dried.

The resulted test 'films are exposed to light and then developed in the same procedures as in Example I to determine photographic characteristics thereof as shown in Table I, wherein a photographic speed is expressed as a relative value based on the white or green light sensitivity of the control compound, which sensitivity is rated as 100.

TABLE 5 Amount added Relative Relative Compound (ca/100 g. speed to speed to used emulsion) white light green light Fog 5 100 135 9. 04 5 0. 03 21 5 100 0. 04: B (control) 5 100 100 0. 0

As is apparent from Table 5, the compounds of the present invention show excellent green light sensitivity even in the photographic emulsion sensitized by use of the gold-sulfur sensitizer.

EXAMPLE 5 lows:

I =CH CH=CH I Q Hi m Sensitization maximum-480 m Absorption maximum-450' m (in MeOI-I) Sensitization maximum630 m Absorption maximum-S40 m (in MeOH) As is clear from Table 6, it is understood that the test emulsion is improved in a light-sensitivity even when the present compound, for example, No. 11 is added thereto in combination with other optical sensitizer, as compared with the cases where these compounds are added alone.

EXAMPLE 6 A light-sensitive, silver iodobromide emulsion for highspeed photographic color negatives which contains by mol of silver iodide is charged with anhydro-5,5'-dichloro-9-ethyl-3,3'-disulfopropyl thiocarbocyanine as a red light sensitizing dye at the amount of 5 mg. per 100 g. of the emulsion to improve spectral sensitivity. Subsequently, 4-chloro-1-hydroxy-Z-n-octylnaphthoamide is dissolved with heating in di-n-butyl phthalate and ethyl acetate. The solution is dispersed in a gelatine solution by use of sodium alkylbenzene sulfonate. The resulting dispersion is added in a given amount to the emulsion. The resulted emulsion is adjusted to pH 6.3 and then coated on a film base to a thickness of 5 microns.

The emulsion layer is further coated with gelatine to form an interlayer. The same silver iodobromide emulsion as in Example 4 is divided into portions of each 100 g. To each portion is added a methanolic solution of the present compound, and successively, l-(2,4,5-trichlorophenyl) -3- 3- (2,4-di-tert. amylphenoxyacetamido benzamidoJ-S-pyrazolone as magenta coupler is dispersed therein according to a similar manner to that of Example 4. The resulted emulsion is adjusted to pH 6.8 and then coated on the said interlayer to a thickness of 6 microns. Further, onto the resulted layer is coated a yellow filter layer comprising colloidal silver. Subsequently, im a silver iodobromide emulsion sensitized with a gold-sulfur sensitizer is dispersed 2-dodecyloxy-benzoyl acetoanilide as a yellow coupler according to the same procedure as in the case of the aforesaid cyan or magenta coupler. The resulted emulsion is adjusted to pH 6.8 and is then coated on the aforesaid yellow filter layer.

The thus obtained multi-layer photosensitive material is exposed to light in the same manner as in Example 4, and then developed with a color developer solution containing as a principal ingredient N-ethyl-N-p-methanesulfonamido-ethyl-3 methylaminoaniline sulfate. After bleaching and fixing according to ordinary method, the resultant material is subjected to color sensitometry. The results are shown in Table 7 wherein a photographic speed is expressed as a relative value of the green light sensitive photographic emulsion! layer containing the present compounds No. 9 and No. 11, based on the green light sensitivity of the control compound A, which sensitivity is rated as 100.

TABLE 7 Amount added Relative (co/ g. speed to emu green Compound use sion) light Fog 9 5 0. 04 ll 5 100 0. M A (control) 5 100 0. 06

Table 7 shows that when the present compounds are used, the green light sensitive emulsion layers of multilayer color sensitive material are less in fogging property.

What we claim is:

1. A light-sensitive, photographic silver halide emulsion which contains, as a sensitizer, a compound of the general formula wherein R is hydrogen or a lower alkyl radical; R and R individually means lower alkyl, lower alkenyl, substituted alkyl selected from the group consisting of hydroxy-, acetoxy-, carboxy-, and sulfo-alkyl or aryl radical; Z is an atomic grouping which can form, together with the adjacent nitrogen and carbon atoms, a fiveor sixmembered heterocyclic ring selected from the group consisting of thiazoles, thiazoline, benzothiazoles, naphthothiazoles, selenazoles, benzoselenazoles, naphthoselenazoles, 3,3-dialkyl-indolenines, benzimidazoles, Z-quinoline, oxazoles, benzoxazoles and naphthoxazoles; Z means oxygen, sulfur or a radical :NR (in which R is lower alkyl or carboxy-alkyl radical); X is an acid residue, provided that X may not exist if the substituted alkyl radical taken for R or R is capable of forming, together with the adjacent nitrogen atom, an intramolecular salt; and m is equal to 0 or 1.

2. A light-sensitive, photographic silver halide emulsion as claimed in claim 1, wherein said compound is represented by the chemical formula 4. A light sensitive, photographic silver halide emulsion as claimed in claim 1, wherein said compound is represented by the chemical formula 2115 (HDsSOr 6. A light-sensitive, photographic silver halide emulsion as claimed in claim 1, wherein said compound is represented by the chemical formula ((611020 C O CH;

((JH2)3SO3" (I32H5 7. A light-sensitive, photographic silver halide emulrepresented by the chemical formula CzHfi V q om c1 GH-CH=CH Cl 01 \N g 211; (HflaSOr References Cited UNITED STATES PATENTS 2,173,486 9/ 1939 Schneider 96137 2,256,163 9/1941 Kumetat et a1 96-137 2,575,018 11/1951 Keyes et a1. 96--1 40 2,719,152 9/1955 ,Jelfreysi 96r1'40' J. TRAVIS BRGWN, Primary Examiner US. Cl; XzR. 96135, 137, 

